INTRODUCTION: The main aim of this study was to differentiate the magnitude of a pilot\'s heart rate variability (HRV) when performing assisted and unassisted flights, as well as simple and complex flight tasks. METHODS: Cardiac monitoring in flights was carried out using a compact, mobile ECG recorder. A frequency analysis of the heart rate (HR) signal was performed to determine the ratio of low-frequency spectral power (LF) to high-frequency spectral power (HF). RESULTS: The LF/HF ratio observed in the zone (M=1.047, SD=0.059) was significantly different than the LF/HF calculated preflight (M=0.877, SD=0.043) and postflight (M=0.793, SD=0.037). There was no main effect of the flight type (unassisted zone flight vs. zone flight with an instructor) on the LF/HF parameter. However, greater psychophysiological load of a pilot was observed in the training zone flights when compared to simple circle flights (main effect of the flight type). CONCLUSIONS: As the LF/HF ratio turned out to be significantly higher in the zone than pre- and postflight, this parameter can be useful for predicting the risk of excessive stress and arousal of pilots during flights. Based on the LF/HF ratio we can also estimate difficulty level of flight tasks, because our research has shown higher values of this parameter in the training zone flights than in simple circle flights.